Number Of Possible Modes Research Articles

Online cycle detection for models with mode-dependent input and output dependencies

In the fields of co-simulation and component-based modelling, designers import models as building blocks to create a composite model that provides more complex functionalities. Modelling tools perform instantaneous cycle detection (ICD) on the composite models having feedback loops to reject the models if the loops are mathematically unsound and to improve simulation performance. In this case, the analysis relies heavily on the availability of dependency information from the imported models. However, the cycle detection problem becomes harder when the model's input to output dependencies are mode-dependent, i.e. changes for certain events generated internally or externally as inputs. The number of possible modes created by composing such models increases significantly and unknown factors such as environmental inputs make the offline (statical) ICD a difficult task. In this paper, an online ICD method is introduced to address this issue for the models used in cyber-physical systems. The method utilises an oracle as a central source of information that can answer whether the individual models can make mode transition without creating instantaneous cycles. The oracle utilises three types of data-structures created offline that are adaptively chosen during online (runtime) depending on the frequency as well as the number of models that make mode transitions. During the analysis, the models used online are stalled from running, resulting in the discrepancy with the physical system. The objective is to detect an absence of the instantaneous cycle while minimising the stall time of the model simulation that is induced from the analysis. The benchmark results show that our method is an adequate alternative to the offline analysis methods and significantly reduces the analysis time.

Phase locking of two limit cycle oscillators with delay coupling.

Mutual phase locking in the system of two limit cycle oscillators with delay coupling is studied. Conditions of phase locking are derived as a result of analysis of a generalized Adler equation. The analytical results are compared with numerical simulation. Depending on the phase shift of the coupling signal propagating between the two oscillators, either in-phase or anti-phase mode of synchronization may arise. The number of possible modes of synchronization increases with the delay time.

Mode set focused hybrid estimation

Estimating the state of a hybrid system means accounting for the mode of operation or failure and the current state of the continuously valued entities concurrently. Existing hybrid estimation schemes try to overcome the problem of an exponentially growing number of possible mode-sequence/continuous-state combinations by merging hypotheses and/or deducing likelihood measures to identify tractable sets of the most likely hypotheses. However, they still suffer from unnecessarily high computational costs as the number of possible modes increases. Hybrid diagnosis schemes, on the other hand, estimate the current mode of operation/failure only, thus leaving the continuous evolution of the system implicit. This paper proposes a novel scheme that uses a combination of both the approaches in order to define posterior transition probabilities between the specified modes of the hybrid system, hence focusing better on relevant hypotheses. In order to demonstrate the effectiveness of the proposed method, the algorithm is applied to a satellite attitude control system and compared with existing hybrid estimation/diagnosis schemes, such as the Interacting Multiple Model (IMM) algorithm, a purely parity based method (HyDiag), and an existing hybrid Mode Estimation (hME) algorithm.

Analysis of TCP performance on multi-hop wireless networks: A cross layer approach

In Multi-Hop Wireless Networks (MHWNs), wireless nodes cooperate to forward traffic between end points that are not in direct communication range. Specifically, traffic is forwarded from a source towards its destination through intermediate nodes that form a wireless multi-hop chain. Researchers have studied the performance of TCP over chains discovering properties such as how the number of hops reduces chain throughput as neighboring links contend for the shared medium. Moreover, the presence of hidden terminals has also been shown to negatively affect performance of example chains. In this paper, we leverage recent characterization of how competing wireless links interact to develop an in-depth analysis of TCP performance over wireless chains. In particular, there are a number of possible modes of interference between competing links with distinct implications on performance and fairness; to our knowledge, this is the first work that studies the impact of these different modes on TCP chain performance. We classify chains according to interference modes considering both the forward (data) and reverse (acknowledgment) traffic. Chain geometry limits the types of chains that arise most frequently in practice. We evaluate TCP performance over the most frequently occurring chain types and observe significant performance differences between chains that have the same hop count. Different four-hop chains, for example, show a throughput difference of up to 25% and a retransmission overhead difference of over 90%. We discuss the implications of these differences on network performance: specifically, route instability and bandwidth usage generated. We extend this analysis to two single-hop TCP flows and quantify the effect of interference interactions between two flows. This study is a first step towards completely understanding the performance of multiple TCP flows over multiple hops in a MHWN.

Finding out about children's literacies in family contexts: Vignettes from Wadestown Kindergarten

Between 2006 and 2009 Wadestown Kindergarten, as a designated Centre of Innovation, investigated multimodal literacies and their roles in communicative competence and meaning making (Simonsen et al., 2009). This focus links with the Communication strand of Te Whariki (Ministry of Education, 1996), which refers to a number of possible modes of expression: images, art, dance, drama, mathematics, movement, rhythm and music (p. 72). We came to define literacies broadly within our study as modes of communication, conceptualisation and meaning making (Simonsen et al. , 2009). Hence the term literacies included traditional print-based and verbal literacies; nontraditional literacies, such as the visual and new information and computer technology (ICT) literacies; and what some would regard as nonliteracies, such as spatial and motor. In common, these literacies represented significant features of children's ways of knowing and communicating. The three research questions for this study were: 1. What does multimodal communicative competence mean in an early childhood setting? 2. How do multimodal literacies interact and support each other at individual, interpersonal and community levels? 3. What is the role of people, places and practices in mediating children's use of multimodal literacies? Our study was exploratory, in the sense that we held an open attitude and genuinely did not know where the investigation would lead. We drew on a range of research methods and perspectives to try to find out about and understand children's favoured literacy modes. In this article, we discuss the immense value of input from parents and whanau in interpreting and analysing data about children's literacies, and the resources and experiences offered in family contexts. We also highlight deepening family engagement in the education programme and more responsive pedagogy that seemed to go hand in hand with our focus on multiple literacies and teachers learning from parents. We argue that as teachers became more open to learning from the insights and experiences of parents and whanau and more appreciative of the multiple ways in which children communicate, they also became more open-minded about parent contributions to the education programme. Method In our Centre of Innovation project we used multiple methods of data collection, including: photographs, videotape recordings and field notes of curriculum events where multiple literacies were evident; case studies of six children; semistructured interviews with participants (parents, children, teachers and research associates); and focus group discussions with kindergarten parents and whanau. Data gathered for the case studies included pedagogical documentation used in the children's assessment portfolios, and video recordings of curriculum events featuring children's literacies. This documentation was gathered over 18 months of the Centre of Innovation project. Parents of case study children were interviewed at the initial and final phases of the project about their child's strengths and preferences as a communicator and family values, strengths and activities. Both these interviews began with us asking parents their views of a video recording of their child, and then of their child's portfolio. Children were asked about their work and portfolios. This article draws primarily on these case study data from children, parents and families. Families: Interpretations of pedagogical documentation, experiences and values Gonzalez and Moll (2002) have argued for a funds of knowledge approach to teachers working with families. Such an approach is based on a premise that people are competent and have knowledge, and their life experiences have given them that knowledge. They argue that through first-hand research experiences with families, we can document this competence and knowledge, and that this engagement leads to many possibilities for positive pedagogical actions (p. …

Studies on waves and instabilities in a plasma sheath formed on the outer surface of a space craft

Using the normal mode analysis, the number of possible modes is obtained in a magnetized inhomogeneous plasma sheath formed during the motion of a space craft which consists of negative ions (due to dust) along with the positive ions and the isothermal electrons. In addition to three propagating modes with phase velocities λ1, λ2, and λ3 such that λ1<λ2<λ3, two types of instabilities with growth rates γ1 and γ2 also occur in such a plasma sheath. The growth rate γ1 is increased with the negative to positive ion density ratio r0, ion temperature T, and obliqueness θ of the magnetic field B0. The growth rate γ2 of the other instability gets lower with the density ratio r0 but gets higher with the temperature T. The growth rate γ2 is sensitive to the temperature T, whereas the growth rate γ1 gets prominently changed with the density ratio r0. The increase in the growth rate γ1 with the obliqueness θ is more pronounced under the effect of stronger magnetic field. On other hand, the phase velocity λ1 shows weak dependence on r0 and T (though it gets larger) but it gets significantly changed (increased) for the larger obliqueness θ. The phase velocity λ2 gets larger with r0, B0, and θ and becomes lower for the higher temperature T. The phase velocity λ3 is decreased for the higher values of r0 and B0 and is increased for the larger values of T and θ.

Guided modes in a grounded slab waveguide of uniaxially anisotropic left‐handed material

AbstractThe guidance conditions of TE and TM waves with both real and imaginary transverse wave numbers in a grounded slab waveguide of uniaxially anisotropic left‐handed material are derived. The mode properties for guided TE waves, such as the existence of guided modes, the number of possible modes and the mode cutoffs are analyzed in different cases graphically. Furthermore, we come into some new conclusions different from the mode properties in an isotropic LHM slab. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1644–1648, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22531

The study of G‐protein coupled receptor oligomerization with computational modeling and bioinformatics

To achieve a structural context for the analysis of G-protein coupled receptor (GPCR) oligomers, molecular modeling must be used to predict the corresponding interaction interfaces. The task is complicated by the paucity of detailed structural data at atomic resolution, and the large number of possible modes in which the bundles of seven transmembrane (TM) segments of the interacting GPCR monomers can be packed together into dimers and/or higher-order oligomers. Approaches and tools offered by bioinformatics can be used to reduce the complexity of this task and, combined with computational modeling, can serve to yield testable predictions for the structural properties of oligomers. Most of the bioinformatics methods take advantage of the evolutionary relation that exists among GPCRs, as expressed in their sequences and measurable in the common elements of their structural and functional features. These common elements are responsible for the presence of detectable patterns of motifs and correlated mutations evident from the alignment of the sequences of these complex biological systems. The decoding of these patterns in terms of structural and functional determinants can provide indications about the most likely interfaces of dimerization/oligomerization of GPCRs. We review here the main approaches from bioinformatics, enhanced by computational molecular modeling, that have been used to predict likely interfaces of dimerization/oligomerization of GPCRs, and compare results from their application to rhodopsin-like GPCRs. A compilation of the most frequently predicted GPCR oligomerization interfaces points to specific regions of TMs 4-6.

A Self-Organized Multiple Model Approach for Neural-Adaptive Control of Jump Nonlinear Systems

A stochastic approach is used to control a multi-modal class of jump nonlinear stochastic systems whose underlying functions are unknown and which can change arbitrarily in time. Gaussian radial basis function neural networks are used to set up a number of local models, each characterising the different nonlinear plant modes. Being unknown, these different modes are identified on-line during control operation without resorting to a separate estimation phase. This entails detecting the occurrence of a mode change during operation. Since no information on the number of possible modes is assumed known, a self-organizing scheme is used to allocate automatically an appropriate number of local models in real time. Function identification, mode change detection and control signal generation are all based on probabilistic techniques utilising concepts of Kalman filtering, the multiple model algorithm and dual control. Simulations are given to show the effectiveness of the system for tracking a reference input, despite jumps in the unknown plant dynamics.

Multiple Equilibrium States in Combined Thermal and Saline Circulation

Abstract Structure and stability of the multiple equilibria of the thermohaline circulation am studied using 2 × 2 and 3 × 2 box models. Thermohaline catastrophe is a shallow phenomenon and its time evolution consists of three stages: the search stage, the catastrophic stage, and the adjustment stage. A 3 × 2 box model is introduced to permit fitting a somewhat less truncated form of freshwater forcing. Although the total number of possible modes of circulation increases quickly as the number of boxes is increased, the grand thermal mode and grand saline mode remain. Some multiple solutions are found to be statistically improbable, and they belong to the so-called minor modes. With the more realistic freshwater forcing appropriate for the present-day North Atlantic, our simple 3 × 2 model predicts that the thermohaline cimulation is near a critical mate, because a small increase in freshwater flux can cause the system to collapse from the present thermally dominated circulation to an intermediate mode of ...

Models of binding of 4′-nitrophenyl α- d-mannopyranoside to the lectin concanavalin A

Molecular models for the complex formed between the lectin concanavalin A (Con A) and the saccharide derivative 4′-nitrophenyl-α- d-mannopyranoside (α-PNM) are presented, combining evidence from 1H-n.m.r. measurements, semi-empirical energy calculations and interactive graphics modelling. The models are in good agreement with the experimental data. Close examination of the models suggests that hydrophobic interactions together with van der Waals interactions and hydrogen bonds contribute to the stability of the complexes. It appears that there is a limited number of possible modes of binding of α-PNM to Con A.

Canonic coupling of oscillators in a ring

AbstractThe paper deals with the phenomenon of coupling of several sinusoidal oscillators. The oscillators are arranged in a ring, and each oscillator affects its next neighbour in the ring. The coupling is unilateral and its main effect is due to variations in phase differences between neighbouring oscillators. The simple approach to the treatment of the behaviour of the coupling and the relative simplicity of the models of oscillators participating in the system enable an analytical solution of the problem to be found without a need to resort to complicated approximate methods. The results are supported by computer simulations. Several modes of dynamic behaviour of the system are identified. The number of possible modes increases with the number of oscillators in the ring. The paper concludes by demonstrating that the present results possess a potential of being useful in analysing some technological and natural systems.

Sodium chloride coupled transport in mammalian nephrons.

A number of possible modes of coupling of sodium chloride transport have been considered, and their roles in the various parts of the renal tubule have been reviewed. Many modes of coupling have been found in various combinations in one or another of the segments. Of special interest are the observations of carrier coupling of sodium to chloride transport in some of the segments, such as the thick ascending limbs of Henle's loop.

The gaseous oxidation of isobutane (part 1)

The oxidation of isobutane has been studied at sub-atmospheric pressures and temperatures in the range 290–430°C. A dramatic change in the kinetics occurs at ca. 330°C and evidence is given which shows that this is due, at least in part, to a change in the chain-branching reactions. Furthermore, in contrast to the exidation of higher molecular weight alkanes the oxidation of isobutane is very dependent on the nature of the reactor surface below ca. 330°C, and it is suggested that this is due to the heterogeneous destruction of the intermediate responsible for branching at these temperatures. Other, smaller changes in the kinetics occur throughout the low temperature combustion region as evidenced by the fine structure of the ignition diagram. The appearance of five lobes in the cool-flame/two-stage ignition boundary shows that a correlation cannot be drawn between these lobes and the number of possible modes of isomerisation of the fuels' alkylperoxy radicals. Evidence is also provided which supports the suggestion that the second stage of the two-stage ignition process is chain-thermal in nature.

The quadrupole ion store (quistor) as a novel source for a mass spectrometer

A system is described in which a quadrupole ion storage trap has been employed as the source for a quadrupole mass filter. A number of possible modes of operation have been examined and results are presented which compare the storage characteristics and mass spectra obtained with established literature data. Some potential areas of application are outlined and the results from a study of ion-molecule reactions in methane included as an example.

The Chemistry of a Reporter Group: 2-Hydroxy-5-nitrobenzyl Bromide

The chemistry of the reaction of 2-hydroxy-5-nitrobenzyl bromide (HNB-Br) with tryptophan ethyl ester to form monosubstitution adducts has been elucidated. The initial compounds are formed by addition at position 3 of the indole ring to form two diastereomeric indolenines. These compounds can then cyclize and rearrange in a number of ways. The absolute stereochemistries of the products have been determined. The 2-hydroxy-5-nitrobenzyl moiety has been shown to form complexes with amino acid esters and the spectral shifts of the complexes can be correlated with the hydrophobicity of the amino acid side chains. The specificity of HNB-Br for tryptophan in proteins can be explained by a combination of a hydrophobic attraction and a specific charge-transfer complex of the quinone methide form of the reagent. The hydrophobic affinity of the HNB group, the specificity of HNB-Br for tryptophan, and the number of potential reaction products of HNB-Br lead to a number of possible modes of reaction of HNB-Br with tryptophan in proteins which enhance the value of the reagent as an environmental probe.

Solid-state laser with vibrating reflector

The temporal behavior of emission, the time-integrated spectral output, and the far-field pattern of a ruby laser have been studied as influenced by the mechanical vibrations of one of the resonator mirrors. It is shown that regular spiking with exponential decay will exist over a wide range of pump power if the following three conditions exist simultaneously: 1) one mirror is slightly tilted, or a lens or a diffusing element is inserted within the cavity; 2) radiation is retained in the resonator by use of a nearly optically closed cavity; and 3) one reflector is vibrating. In this case, the spectral output consists not of sharp lines, but of a few broad bands. Consequently, oscillation in closely spaced transverse modes is produced by the vibrating mirror. If one of the above conditions is not fulfilled, irregular spiking occurs and the spectral output contains sharp lines whose frequencies are multiples of the axial mode spacing and whose number depends directly upon the pump power. Regular spiking permits an experimental test of theoretical models. The plot of the decay time of the regular spiking envelope versus normalized pump power has ascending and descending branches and is in excellent agreement with the expanded Statz-de Mars theory, which takes into account a large mode number and the influence of spontaneous emission. Parameter of the family of curves is the ratio : number of existing resonator modes to total number of possible modes (for the same bandwidth) that is approximately equal to the solid angle of laser radiation divided by the solid angle 4 π. Finally, the experimental values for the period of the spike train agree so well with theory that they can be used to determine the total mode number and the Einstein coefficient <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</tex> .

Electromagnetic Fields in a Homogeneous, Nonisotropic Universe

A solution of the Einstein-Maxwell equations is derived that represents a closed universe of topology S/sup 3 / x R, filled with gravitational and electromagnetic radiation. The lowest of the large number of possible modes of radiation in such a universe is considered. This mode has maximum symmetry consistent with the existence of a vector field; the universe is homogeneous but not isotropic, and is therefore a generalization of one of the solutions discussed by Taub. It is possible to solve explicitly for the metric coefficients. Some of the physical properties of the solution are discussed. (auth)

An Experiment in Problem Solving

Trial-and-error problems are described in terms of “stimulus” difficulty, which is a measure of the number of possible modes of response left to the individual when all the information given is taken into account; and “phenomenal” difficulty, which is a measure derived from the individual's performance. An experiment is described in which three types of problem were presented to human subjects. In all three problems the stimulus difficulty was calculable, stage by stage, in the solution. The problems differed in this stimulus difficulty and also in the qualitative nature of the information provided—from unequivocal to conditional. It is shown that the qualitative difference of the nature of the information bears most relationship to phenomenal difficulty. Some observations are made on the modes of solution adopted, and further experimental work is suggested.

Study of the Admittance Spectra of Piezoelectric Plates in Thickness-Shear Vibration

A thin square plate vibrating in thickness shear has an infinite number of possible modes of vibration characterized by different standing-wave formation along the three major axes of the plate. When the plate is piezoelectric and connected into an electric circuit, the observed admittance spectrum may be further complicated by coupling between the thickness-shear modes and modes of other types of vibration, such as flexure or face-shear vibration. This paper describes observations made with a spectrum analyzer specially designed for the purpose. Two kinds of observations are made: (a) with the plate resing on a flat electrode, while the upper electrode is a small steel ball, which can be moved to any point of the surface of the plate, (b) with the plate mounted between electrodes of standard type. The first kind makes it possible to identify the modes and to determine their frequencies and their amplitude distribution over the surface. The second kind indicates to what extent the various modes are coupled to the electrical circuit in conventional operation. Some results are reported as to the effect of variation in thickness contour, ratio of width to thickness, and clamping conditions of the plate. The work is being done under a contract with U. S. Signal Corps.